1. Field of the Invention
This invention relates to a metal film coated body, an adhesive layer and an adhesive, and more particularly proposes an adhesive and an adhesive layer having an excellent toughness without lowering heat resistance, electric insulation property and chemical stability and various metal film coated bodies having an excellent adhesion property between a substrate and a coated metal.
2. Description of Background Information
Recently, printed circuit boards and printed wiring substrates mounting LSI are required to have high densification and high reliability through fine pattern corresponding to miniaturization and high-speed performance of electron equipments with the advance of electron industry.
As a method of forming the conductor onto the printed wiring substrate, there is recently noticed an additive method wherein an adhesive is applied onto a surface of a substrate to form an adhesive layer and thereafter the surface of the substrate is roughened and subjected to an electroless plating.
According to this method, the conductor is formed by electroless plating after the formation of a resist, so that it has a merit that conductor wiring having high density and pattern accuracy can be produced with a low cost as compared with an etched foil method conducting the formation of pattern through etching (subtractive method).
In the additive method, there have hitherto been known a method in which fine unevenness is formed on the conductor-forming surface side of the adhesive layer through a chemical etching as a means for improving the adhesion property between conductor and adhesive layer (hereinafter explained a xe2x80x9cpeel strengthxe2x80x9d).
In recent additive type printed circuit board requiring the formation of wiring with high density and pattern accuracy, however, it is required to make smaller anchor formed by surface roughening of the adhesive layer in order to precisely form the fine pattern of the resist. Therefore, as the anchor becomes small, the breaking area is small, so that there is caused a problem that the peel strength considerably lowers.
On the other hand, metallic parts are recently replaced with resin parts by the improvement of engineering plastics in automobile and transportation equipment related fields, electrical and electron parts and machine related fields, household article related field, civil engineering field and medical field.
For instance, there are mentioned housing and fixed ring of a camera using polycarbonate, bearing made from polyacetal and the like. Further, gear or the like made from super-high molecular weight polyethylene is developed.
In these resin parts, however, it might be required to cover the surface of the part with a metal film from viewpoints of design, corrosion resistance, wear resistance and the like.
As means for covering the resin surface with the metal film, there has hitherto been proposed a method in which an adhesive layer is formed on the surface of the resin substrate and the surface of the adhesive layer is roughened and coated with the metal film.
For example, JP-B-58-44709 discloses a method wherein an adhesive for electroless plating consisting of acrylonitrile butadiene rubber and epoxy resin is applied onto a surface of an insulative substrate and then the epoxy resin portion on the surface of the adhesive layer is dissolved and removed to roughen the surface and thereafter electroless plating is conducted to form a metal film coating.
Further, JP-A-61-276875 discloses a method wherein an adhesive for electroless plating obtained by dispersing fine powder of heat-resistant resin into heat-resistant resin matrix is applied onto the substrate and then the surface thereof is roughened by treating the fine powder of the heat-resistant resin with an oxidizing agent and thereafter the electroless plating is conducted.
In the engineering plastic (substrate resin) coated with the metal film through the adhesive layer, however, there were observed problems that cracks are caused due to the difference in thermal expansion coefficient between the substrate resin and the adhesive layer in heat cycle and that cracks are created in the adhesive layer itself at the time of generating stress.
In order to solve these problems, there is a method of increasing the strength of the coating metal or the heat-resistant resin matrix constituting the adhesive. According to the inventors"" experiments, however, it has been confirmed that the peeling of the electroless plated film constituting the coating metal is created by the breakage of the heat-resistant resin matrix in the conventional technique using copper as the coating metal and the thermosetting resin or photosensitive resin as the heat-resistant resin matrix constituting the adhesive. That is, it has been noticed that the strength of the heat-resistant resin matrix constituting the adhesive is lacking as a cause of lowering the bonding strength. Further, it has been confirmed that the cause of cracking in the heat cycle or in the generation of stress is also the poor strength of the heat-resistant resin matrix.
In order to solve the aforementioned various problems in the conventional technique, therefore, it is an object of the invention to strengthen the heat-resistant resin matrix constituting the adhesive without lowering the heat resistance, electric insulation property and chemical stability.
It is another object of the invention to provide an adhesive layer having an excellent adhesion property to the coating metal.
It is the other object of the invention to establish the technique capable of stably providing various metal film coatings for printed circuit board having an improved peel strength even in wirings having high density and high pattern accuracy and other industrial parts.
The inventors have made various studies with respect to the improvement of the strength in the heat-resistant resin matrix constituting the adhesive in order to attain the above objects. As a result, it has been found that a mixed resin of an uncured thermosetting resin containing a resin substituted at a part of its functional group with a photosensitive group and/or an uncured photosensitive resin and a thermoplastic resin is used as a heat-resistant resin matrix constituting the adhesive and a resin composite obtained by curing this resin is used as an adhesive layer, whereby a metal film coated body such as printed wiring substrate or the like having an excellent adhesion strength to conductor metal can be provided even if anchor depth formed by roughening treatment is small, and the invention has been accomplished.
That is,
(1) The adhesive according to the invention is an adhesive obtained by dispersing a dissolution-removable or decomposition-removable particulate substance into an uncured heat-resistant resin matrix, in which the heat-resistant resin matrix is a compatibility-adjusted resin mixture consisting of a thermoplastic resin and at least one or two resins selected from an uncured thermosetting resin containing a resin substituted at a part of its functional group with a photosensitive group (hereinafter referred to as uncured thermosetting resin simply) and an uncured photosensitive resin. This resin mixture is preferable to be compatible state by dissolving in a solvent or incompatible state. The word xe2x80x9ccompatiblexe2x80x9d as used herein refers to two or more components being miscible with each other.
When the resin mixture is at the compatible state, quasi-homogeneous compatible structure, co-continuous phase structure or spherical domain structure as mentioned later can be obtained by adjusting phase-separation rate and curing rate in the curing of the mixture.
When the resin mixture is at the incompatible state, spherical domain structure can be obtained by curing the mixture as it is.
As the dissolution-removable particulate substance, it is desirable to use at least one particle selected from inorganic particles, metal particles, elastomer particles, alkali-soluble resin particles and solvent-soluble resin particles.
As the decomposition-removable particulate substance, it is desirable to use a suspension-polymerized low crosslinking amino resin or the like.
In the invention, the term xe2x80x9cdissolution-removalxe2x80x9d means that the dissolution and decomposition of the particulate substance are caused by chemical action using a roughening solution such as acid, alkali, oxidizing agent, water, organic solvent or the like, while the term xe2x80x9cdecomposition-removalxe2x80x9d means that the decomposition of the particulate substance is caused by heating, pressurizing, or atmosphere adjustment such as humidity adjustment or the like without using the roughening solution.
Furthermore, the xe2x80x9cresin mixture of the thermoplastic resin and at least one or two resins selected from thermosetting resins and photosensitive resinsxe2x80x9d used in the invention means {circle around (1)} a resin mixture of thermosetting resin and thermoplastic resin, {circle around (2)} a resin mixture of photosensitive resin and thermoplastic resin, or {circle around (3)} a resin mixture of thermosetting resin, photosensitive resin and thermoplastic resin.
Another adhesive according to the invention is an adhesive obtained by dispersing into an uncured heat-resistant resin matrix a resin solution not compatible with the matrix before curing and dissolution removable after curing, characterized in that the heat-resistant resin matrix is a compatibility-adjusted resin mixture of a thermoplastic resin and at least one or two resins selected from uncured thermosetting resins and uncured photosensitive resins.
The other adhesive according to the invention is an adhesive obtained by mixing an uncured heat-resistant resin matrix with a resin solution compatible with the matrix before curing and dissolution removable by phase separation after curing, characterized in that the heat-resistant matrix is a compatibility-adjusted resin mixture of a thermoplastic resin and at least one or two resins selected from uncured thermosetting resins and uncured photosensitive resins.
When such a resin mixture is at the compatible state, quasi-homogeneous compatible structure, co-continuous phase structure or spherical domain structure as mentioned later can be obtained by adjusting phase-separation rate and curing rate in the curing of the mixture.
When the resin mixture is at the incompatible state, spherical domain structure can be obtained by curing the mixture as it is.
(2) The adhesive layer according to the invention is an adhesive layer formed on a substrate and having a roughened surface, characterized in that said layer is formed by dispersing a dissolution-removable or decomposition-removable granular substance into a cured heat-resistant resin matrix being a resin composite consisting of a thermoplastic resin and at least one or two resins selected from a thermosetting resin containing a resin substituted at a part of its functional group with a photosensitive group (hereinafter referred to as uncured thermosetting resin simply) and an uncured photosensitive resin. This resin composite is preferable to form a quasi-homogeneous compatible structure, co-continuous phase structure or spherical domain structure.
As the dissolution-removable particulate substance, it is desirable to use at least one particle selected from inorganic particles, metal particles, elastomer particles, alkali-soluble resin particles and solvent-soluble resin particles.
As the decomposition-removable particulate substance, it is desirable to use a suspension-polymerized low crosslinking amino resin or the like.
The other adhesive layer according to the invention is an adhesive layer formed on a substrate and having a roughened surface, characterized in that said layer is formed by dispersing a dissolution-removable resin into a cured heat-resistant resin matrix being a resin composite consisting of a thermoplastic resin and at least one or two resins selected from a thermosetting resin and a photosensitive resin in form of lands to form a sea-land structure. This resin composite is preferable to form a quasi-homogeneous compatible structure, co-continuous phase structure or spherical domain structure.
As the dissolution-removable resin, it is desirable to use a resin not compatible with the uncured heat-resistant resin matrix before the curing and forming xe2x80x9csea-land structurexe2x80x9d with this resin matrix at inhomogeneous state after the curing, and a resin compatible with the uncured heat-resistant resin matrix before the curing, causing phase separation from this resin matrix during the curing and forming xe2x80x9csea-land structurexe2x80x9d with the resin matrix at inhomogeneous state after the curing.
The phase separation during the curing includes {circle around (1)}. phase separation created by the curing of the matrix resin, {circle around (2)}. phase separation created by the curing of both the matrix and the dissolution removable resin, and {circle around (3)}. phase separation created by heat (temperature) added in the curing and fixation of phase by the curing.
Moreover, the term xe2x80x9csea-land structurexe2x80x9d used in the invention means that the heat-resistant resin matrix forms a sea and high concentration portions of the dissolution-removable resin are existent in the sea at an inhomogeneous concentration state in form of lands, in which the boundary between sea and land is unclear. These lands may be separated from each other in the sea, or some of lands may be continuous.
In such an adhesive layer, the roughened surface is formed by dissolving or decomposing off the dissolution-removable or decomposition-removable particulate substance or the dissolution-removable resin with land structure from the surface of the adhesive layer.
As the substrate, use may be made of printed circuit board provided with conductor circuit and industrially applicable ones of various shapes such as fiber-shaped, rod-shaped, spherical-shaped and the like.
(3) The metal film adhered body according to the invention comprises a substrate, an adhesive layer having a roughened surface at its side to be coated with a metal, and a metal film arranged on the roughened surface of the adhesive layer, characterized in that the adhesive layer is formed by dispersing a dissolution-removable or decomposition-removable particulate substance into a cured heat-resistant resin matrix being a resin composite consisting of a thermoplastic resin and at least one or two resins selected from a thermosetting resin containing a resin substituted at a part of its functional group with a photosensitive group (hereinafter referred to as uncured thermosetting resin simply) and an uncured photosensitive resin. This resin composite is preferable to form a quasi-homogeneous compatible structure, co-continuous phase structure or spherical domain structure.
As the dissolution-removable particulate substance, it is desirable to use at least one particle selected from inorganic particles, metal particles, elastomer particles, alkali-soluble resin particles and solvent-soluble resin particles.
As the decomposition-removable particulate substance, it is desirable to use a suspension-polymerized low crosslinking amino resin or the like.
The other metal film coated body according to the invention comprises a substrate, an adhesive layer having a roughened surface at its side to be coated with a metal, and a metal film arranged on the roughened surface of the adhesive layer, characterized in that the adhesive layer is formed by dispersing a dissolution-removable resin into a cured heat-resistant resin matrix being a resin composite consisting of a thermoplastic resin and at least one or two resins selected from a thermosetting resin and a photosensitive resin in form of lands to form a sea-land structure. This resin composite is preferable to form a quasi-homogeneous compatible structure, co-continuous phase structure or spherical domain structure.
As the dissolution-removable resin, it is desirable to use a resin not compatible with the uncured heat resistant resin matrix before the curing and forming xe2x80x9csea-land structurexe2x80x9d with this resin matrix at inhomogeneous state after the curing, and a resin compatible with the uncured heat-resistant resin matrix before the curing, causing phase separation from this resin matrix during the curing and forming xe2x80x9csea-land structurexe2x80x9d with the resin matrix at inhomogeneous state after the curing.
As the substrate, use may be made of printed circuit board provided with conductor circuit and industrially applicable ones of various shapes such as fiber-shaped, rod-shaped, spherical-shaped and the like.
In the metal film coated body according to the invention, the board is used as a substrate and a coated metal is etched, if necessary, or a metal is coated in form of pattern to form a printed circuit board.
Such a printed circuit board is a printed circuit board wherein an adhesive layer formed by dispersing the dissolution-removable or decomposition-removable particulate substance into the cured heat-resistant resin matrix is, for example, formed on the substrate and the roughened surface is formed on the surface of the adhesive layer to be provided with the conductor and further the conductor circuit is arranged on the roughened surface, characterized in that the heat-resistant resin matrix is a resin composite consisting of a thermoplastic resin and at least one or two resins selected from thermosetting resin and photosensitive resin. The resin composite is preferable to form a quasi-homogeneous compatible structure, co-continuous phase structure or spherical domain structure.
The other printed circuit board comprises a substrate, an adhesive layer formed thereon by dispersing lands of a dissolution-removable resin into a sea of a cured heat-resistant resin matrix consisting of a resin composite of a thermoplastic resin and at least one or two resins selected from thermosetting resin and photosensitive resin to form a sea-land structure and provided with a conductor-forming roughened surface and a conductor circuit arranged on the roughened surface, characterized in that the heat-resistant resin matrix is a resin composite of a thermoplastic resin and a thermosetting resin and/or a photosensitive resin. The resin composite is preferable to form a quasi-homogeneous compatible structure, co-continuous phase structure or spherical domain structure.